State-of-Arts of Mechanics of Rolling Contact and Its Application to Analysis of the Interactions between Wheel and Rail

A few typical models of theory on rolling contact of bodies are reviewed, and the advantages and disadvantages in the applications to the dynamics of railway vehicles and the wheel/rail rolling contact are discussed in detail in the present paper.

Effects of Lateral Motion on the Creep Forces in Wheel/Rail Rolling Contact

The influences of the lateral motion of a single wheelset running on a tangent railway on the creepages and creep forces between wheel and rail are investigated with numerical methods. The effect of the yaw motion of wheelset is neglected in the analysis, and Kalker’s theory of three dimensional elastic bodies in rolling contact is employed to analyze the creep forces in the wheel/rail rolling contact with Non Hertzian form.

An integrated approach for the optimization of wheel-rail contact force measurement systems

A comprehension of railway dynamic behavior implies the measure of wheel-rail contact forces which are affected by disturbances and errors that are often difficult to be quantified. In this study, a benchmark test case is proposed, and a bogie with a layout used on some European locomotives such as SIEMENS El90 is studied. In this layout, an additional shaft on which brake disks are installed is used to transmit the braking torque to the wheelset through a single-stage gearbox. Using a mixed approach based on finite element techniques and statistical considerations, it is possible to evaluate an optimal layout for strain gauge positioning and to optimize the measurement system to diminish the effects of noise and disturbance. We also conducted preliminary evaluations on the precision and frequency response of the proposed system.

Modeling of Energy Processes in Wheel-Rail Contacts Operating under Influence of Periodic Discontinuous Forces

In this paper we present new numerical simulation approaches for determining the energy processes under periodic conditions caused by time-discontinuous forces in the wheel-rail contacts. The main advantage of the presented method is the total elimination of frequency analysis, which in effect introduces important simplifications in the identification of the effects in the contact. The second important feature is the fact that the method is based on the analysis of appropriate loops on the energy phase plane leading to an easy estimation of the rail strength through the evaluation of the loop’s area. That model based simulation in the applied dynamics relies on advanced methods for model setup, robust and efficient numerical solution techniques and powerful simulation tools for practical applications. Fundamental properties of contact displacements of the rail surface have been considered on the basis of the newly established method. The contact zone between railway wheels and the rail surfaces made of bulk materials is perceived as strong enough to resist the normal (vertical) forces introduced by heavy loads and the dynamic response induced by track and wheel irregularities. The analysis is carried out for a wheel running on an elastic rail rested on sleepers arranged on completely rigid foundation. The equations of displacement motion are established through the application of the Lagrange equations approach. The established model of the wheel-rail contact dynamics has been applied to that same roll plane but with taking into account a nonlinear characteristic of the sleeper with respect to the ground. Attention then is focused completely on the modeling of the energy absorbed by the rail. The applied method employs the energy state variables as time functions leading to determine the susceptibility of a given contact on the strength induced by the rail roll.

Simulation of wheel and rail profile wear:a review of numerical models

The development of numerical models able to compute the wheel and rail profile wear is essential to improve the scheduling of maintenance operations required to restore the original profile shapes.This work surveys the main numerical models in the literature for the evaluation of the uniform wear of wheel and rail profiles.The standard structure of these tools includes a multibody simulation of the wheel-track coupled dynamics and a wear module implementing an experimental wear law.Therefore,the models are classified according to the strategy adopted for the worn profile update,ranging from models performing a single computation to models based on an online communication between the dynamic and wear modules.Nevertheless,the most common strategy nowadays relies on an iteration of dynamic simulations in which the profiles are left unchanged,with co-simulation techniques often adopted to increase the computational performances.Work is still needed to improve the accuracy of the current models.New experimental campaigns should be carried out to obtain refined wear coefficients and models,while strategies for the evaluation of both longitudinal and transversal wear,also considering the effects of tread braking,should be implemented to obtain accurate damage models.

Multi-Body Dynamics Modeling of Heavy Goods Vehicle-Rail Interaction

Based on the principle of vehicle-track coupling dynamics, SIMPACK multi-body dynamics software is used to establish a C80 wagon line-coupled multi-body dynamics model with 73 degrees of freedom. And the reasonableness of the line-coupled dynamics model is verified by using the maximum residual acceleration, the nonlinear critical speed of the wagon. The experimental results show that the established vehicle line coupling dynamics model meets the requirements of vehicle line coupling dynamics modeling.

Simulation on derailment base on a new wheel-rail contact method

The simulation package for special research on derailment of high speed vehicle is established.The process of derailment is different from other behaviors of vehicle dynamics because of large lateral displacement of wheelsets.To get correct results,a new fast algorithm to computing contact force is adopted and the exact geometry analysis is necessary to judge derailment happened.Variation of contact condition and coefficient of friction with speeds are also considered into vehicle-track coupled model.The structure of the package is presented in detail.The results are particular emphasis on investigation influence of maximum track defect,critical vehicle speed and various contact condition on derailment.The simulation can also be used to define the most risk factor leading to derailment.

A Novel Model for Describing Rail Weld Irregularities and Predicting Wheel-Rail Forces Using a Machine Learning Approach

Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.

Multi-point Contact of the High-speed Vehicle-turnout System Dynamics

The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. However, the above problems are not well solved currently because of having the difficulties in how to determine the multi-contact, to preciously present the changeable profiles of the rails and to establish an accurate spatial turnout system dynamics model. Based on a high-speed vehicle-turnout coupled model in which the track is modeled as flexible with rails and sleepers represented by beams, the line tracing extreme point method is introduced to investigate the wheel-rail multiple contact conditions and the key sections of the blade rail, longer nose rail, shorter rail in the switch and nose rail area are discretized to represent the varying profiles of rails in the turnout. The dynamic interaction between the vehicle and turnout is simulated for cases of the vehicle divergently passing the turnout and the multi-point contact is obtained. The tracks of the contact patches on the top of the rails are presented and the wheel-rail impact forces are offered in comparison with the contact patches transference on the rails. The numerical simulation results indicate that the length of two-point contact occurrence of a worn wheel profile and rails is longer than that of the new wheel profile and rails; The two-point contact definitely occurs in the switch and crossing area. Generally, three-point contact doesn’t occur for the new rail profile, which is testified by the wheel-rails interpolation distance and the first order derivative function of the tracing line extreme points. The presented research is not only helpful to optimize the structure of the turnout, but also useful to lower the dynamics of the high speed vehicle-turnout system.

A New Method for Modelling and Simulation of the Dynamic Behaviour of the Wheel-rail contact

This paper presents a new method for modelling and simulation of the dynamic behaviour of the wheel-rail contact. The proposed dynamic wheel-rail contact model comprises wheel-rail contact geometry, normal contact problem, tangential contact problem and wheelset dynamic behaviour on the track. This two-degree of freedom model takes into account the lateral displacement of the wheelset and the yaw angle. Single wheel tread rail contact is considered for all simulations and Kalker’s linear theory and heuristic non-linear creep models are employed. The second order differential equations are reduced to first order and the forward velocity of the wheelset is increased until the wheelset critical velocity is reached. This approach does not require solving mathematical equations in order to estimate the critical velocity of the dynamic wheel-rail contact model. The mathematical model is implemented in Matlab using numerical differentiation method. The simulated results compare well with the estimated results based on classical theory related to the dynamic behaviour of rail-wheel contact so the model is validated.

基于GPD理论和百分位数阈值法的轮轨力极值估计与动力系数研究

在高速铁路无砟轨道结构设计和检算时,列车荷载设计值是关键的设计参数之一。基于GPD理论,研究全波段不平顺激励下的轮轨力极值估计方法,并与脉冲激励下的结果对比,为无砟轨道结构设计和相关规范的完善提供依据。结果表明:采用百分位数法选取阈值时,应对样本分簇以提高样本之间的独立性和轮轨力极值估计的精度;提出结合百分位数阈值的形状参数筛选法进行轮轨力极值估计,确定了每簇样本量大小和形状参数区间;样本量宜取3×10^(5)~5×10^(5)个,百分位数阈值宜取50%~98%,且以轮轨力极值估计值的均值作为最终的轮轨力极值估计值;列车速度为250~400 km/h的列车荷载设计值动力系数分别为2.2、2.4、2.6和2.8。

考虑材料温变特性的三维轮轨接触热分析

为研究材料温变特性对轮轨接触行为和摩擦温升的影响,提出了一种考虑材料温变特性的三维轮轨热力耦合模型,能够考虑纵、横向蠕滑率和自旋的影响,更为真实地模拟轮轨系统的服役状态.首先,研究了热力耦合建模方式对轮轨界面摩擦温升及接触应力的影响;随后,将该模型应用于地铁小半径曲线处车辆-轨道相互作用模拟.结果表明:当轮轨界面温度达到450℃时,轮轨接触应力显著降低,降幅可达20%;考虑热力耦合建模后,轮轨界面的预测温升明显低于不考虑热力耦合建模时的结果,在蠕滑率为0.16时,两者的差异可达51%;地铁车辆在小半径曲线线路上运行时轮轨摩擦温升因过大的蠕滑率与自旋会急剧增大到750℃,应考虑轮轨热力耦合建模以避免过高估计轮轨摩擦温升以及轮轨接触应力.

轨底坡耦合轮径差对地铁车辆动力学性能及轮轨接触特性的影响

为了研究轨底坡耦合轮径差对于地铁车辆动力学性能及轮轨接触特性的影响规律,设置了3种轨底坡工况(1/20、1/30和1/40)和5种轮径差工况,通过建立地铁车辆动力学仿真模型和轮轨接触三维弹性有限元模型,分析轨底坡耦合轮径差对地铁车辆直线平稳性和曲线通过性能的影响。结果表明:直线路段车辆平稳性指标受到轮径差变化的影响大于轨底坡变化的影响,轮轨等效应力和接触应力会随着轮径差的增加而增大;曲线路段的各个动力学指标会随着轮径差的增加而增大;综合考虑动力学指标和轮轨接触特性,直线路段下尽量减少使用1/20轨底坡;曲线路段下,可以选择1/30轨底坡,减少轮径差对车辆的影响。

轨底坡耦合车轮动态型面下地铁轮轨接触特性

为探究地铁车轮型面动态变化与轨底坡设置的关系,跟踪测试了运行里程5万、8万、14万公里车轮磨耗型面,研究轨底坡耦合车轮动态型面时的轮轨接触特性;以车辆动力学理论为依据,根据实测地铁车辆参数,建立了车辆系统动力学模型;基于轮轨接触几何关系和非赫兹滚动接触理论,建立了轮轨滚动接触计算模型;以轮轨接触点和接触位置、滚动圆半径差、接触角、等效锥度、蠕滑率、接触斑面积和最大接触压力作为轮轨接触几何和力学性能指标,分析轨底坡耦合车轮动态型面对轮轨接触特性的影响规律。结果表明:LM标准型面和5万公里车轮磨耗型面与1/20轨底坡匹配时轮轨接触点分布均匀;随着运行里程增加,车轮磨耗型面变化,轮轨接触恶化,轮对横移量4 mm下,8万和14万公里车轮磨耗型面与1/20轨底坡匹配时各指标出现断点。

轮轨接触点位置变化对测力轮对测量影响及其补偿方法

[目的]列车运行过程中,轮对存在随机振动,导致轮轨接触点位置发生变化,进而影响轮轨力的测量结果。为了解决该问题,提出一种测量补偿方法。[方法]介绍了轮轨接触点位置变化对测力轮的影响;介绍了轮轨接触点位置变化后,轮轨力测量的补偿方案;通过仿真分析,验证考虑轮轨接触点位置变化的轮轨力测量补偿方案的有效性。[结果及结论]添加美国五级轨道不平顺谱激励后,轮轨接触点位置最大偏移量为17.53 mm,垂向力最大相对误差达到了22.85%;采用所提测量补偿方法后,轮轨垂向力最大相对误差为8.02%,测量精度明显提高。叠加尖弯不平顺谱后,脱轨系数最大达到了1.016 8,超过允许限度;采用无偏移标定系数计算出的脱轨系数为0.347 7,采用所提补偿方法计算出的脱轨系数为0.962 2,说明该方法能够更准确地反映出列车的运行安全状态。

等效锥度非线性研究及其在踏面设计中的应用

为研究等效锥度非线性特性对车辆系统动力学和磨耗性能的影响,提出可以用于踏面优化设计的非线性特性建议指标。通过对轮轨关系进行细致推导,应用踏面逆向设计快速递推算法,得到具有不同等效锥度非线性特性的踏面,对不同踏面的轮轨关系进行分析。建立车辆系统动力学模型和基于Archard理论的磨耗预测模型,对不同非线性特性踏面的临界速度、横向平稳性、磨耗性能进行对比分析。研究结果表明:非线性因子值过高或过低都会导致临界速度下降,但该指标过高对临界速度影响更大,最大降幅可达20%;等效锥度非线性特性还会影响到踏面的磨耗发展,踏面的初始非线性因子越高,名义等效锥度在磨耗过程中的增长越慢,对延长车轮服役周期是有利的。综合动力学性能及磨耗性能,建议高速列车踏面的非线性因子应取尽可能接近于0的负值。在这一结论的指导下,对S1002CN踏面进行优化设计,得到名义等效锥度为0.1,等效锥度非线性因子为0.013(与S1002CN持平)、-0.002的优化踏面S1002CN_opt1、S1002CN_opt2,优化踏面S1002CN_opt2与S1002CN相比临界速度和横向平稳性有所优化,同时磨耗性能也有所提升。S1002CN_opt2与S1002CN_opt1之间的等效锥度非线性关系在动力学性能及磨耗性能中的表现证明以等效锥度非线性因子限值指导踏面进行优化设计的可行性,研究结果可为踏面设计及轮轨关系研究提供参考。

基于车辆动力学的铁路轨道曲线啸叫时域模型

曲线啸叫是轮轨切向黏滑接触、轮轨动力学和通过曲线时车辆运行状态的综合结果。为综合研究曲线啸叫的影响因素,基于整车车辆多体动力学,并采用改进的轮轨接触力计算方法,建立了曲线啸叫时域模型。在接触力计算中,使用了离散接触模型,为引入下落摩擦机理,在切向力计算中使用迭代方法确定摩擦系数和接触力,使用模态叠加法计算车轮振动响应,采用无限元方法计算车轮声辐射。研究不同曲线半径和通过速度下,曲线段轮轨间接触力的变化及接触区的黏着-滑动状态,对车轮振动特性进行分析,并研究了车轮声学响应。研究发现,在下落摩擦和整车车辆运动状态的共同作用下会出现啸叫现象;曲线段轮轨间的法向力和切向力均会出现振荡,接触区呈现黏滑振荡状态;车轮振动速度谱的峰值频率与车轮特征模态相近,车轮轴向和径向模态的高幅振动是高频啸叫的原因之一。啸叫现象主要出现在前轮上,相同工况下,前后轮声压级相差近20 dB,车辆速度和曲线半径对啸叫程度有明显影响,当车辆的曲线通过速度为60 km/h时,小曲线半径会出现严重啸叫现象;当曲线半径由200 m增大到400 m时,最大声压级降低34 dB;曲线通过速度由60 km/h降至40 km/h时,最大声压级下降13 dB。

轮轨作用力与垂向载荷位置的轨旁识别法研究

为解决现有轮轨作用力识别方法存在的制作工艺复杂、制作成本高且无法实现轮轨接触位置测量的问题,提出一种测量水平横向和垂向轮轨接触力大小以及垂向载荷偏心位置新的轨旁识别方法。基于轮轨接触多元载荷解耦建立横向和垂向轮轨接触力大小和垂向接触力作用位置与钢轨腹板两侧垂向应变和、应变差的理论关系模型,依此得到基于腹板两侧应变运算的轮轨力大小与位置识别反算模型。设计了作用在腹板左、右两侧的正交组合式应变阵列电桥用于识别轮轨接触载荷在轨道腹板位置的应变响应,所设计的阵列电桥在实现腹板两侧应变的四则运算的同时兼顾温度自补偿。通过加载标定试验获取了多元载荷与腹板两侧应变输出之间的关系系数。通过随机组合加载试验验证了水平横向和垂向轮轨接触力大小与垂向接触力作用位置的识别精度,并在实车试验中对比分析了新型轮轨接触力测量方法与国标轮轨载荷测量方法对轮轨接触力大小的识别精度。研究结果表明:提出的轮轨接触力识别方法对接触力大小的识别误差在6.2%以内、对垂向载荷偏心位置的识别误差在7.6%以内,实现了使用轨旁识别方法对轮轨接触力大小和垂向载荷偏心位置的准确识别。研究结果为进一步保障钢轨服役可靠性的精准评估提供科学数据支撑。

高速铁路大跨度连续斜拉桥上梁端一体化装置性能研究

目前大跨度斜拉桥上铺设无缝线路,梁端处需设置梁端伸缩装置和钢轨伸缩调节器以降低钢轨产生较大的附加应力,但此结构无法协调较大的梁轨相对位移,应用范围有限。为此,提出了一种梁端一体化装置结构,能适用于较大的梁缝伸缩情况且伸缩阻力较小,经过现场应用效果良好。针对时速350 km下高速列车能够平稳通过大跨度斜拉桥无缝线路梁端的要求,建立了相关三维梁端车-线-桥耦合模型,确定了轮轨接触关系,验证该结构在大跨度斜拉桥下对于高速列车平稳运行的适用性。结果表明:温度和梁端转角作用下钢轨会产生一定变形,钢轨垂向变形大于横向变形,最大垂向位移达到15.71 mm。对比仅施加德国低干扰不平顺谱,叠加温度或梁端转角变形后行车过程中的梁端一体化装置动力响应增大,且对钢枕振动垂向加速度的影响较为明显,从38.92 m·s^(-2)上升至48.69 m·s^(-2),增加25.1%。相比之下,极限拉伸状态比极限压缩状态下行车过程中的梁端一体化装置结构响应大,钢枕垂向加速度从40.64 m·s^(-2)上升至62.39 m·s^(-2),增加53.5%,应在高温拉伸状态下对梁端一体化装置性能进行定期检测。梁端一体化装置在以上工况下的响应均满足标准规范要求,本研究可为其在列车高速运行通过大跨度斜拉桥梁端时的铺设提供参考。

基于5G毫米波的高速动车组运行品质轨旁动态监测系统设备研制

为了更好地监测高速动车组车轮多边形磨耗,保障运行品质,针对高速动车组轮对状态地面式动态检测需求,设计开发了一种基于5G毫米波的高速动车组运行品质轨旁动态监测系统设备并给出了整体安装方案。该设备主要由不打孔剪力传感器和结构-耦合二维垫板传感器构成的力学测试平台、5G毫米波无线数据采集模块、5G毫米波基站、图像车号相机、边缘计算设备箱、太阳能供电装置等组成。在测量原理上,该设备采用全连续的“剪力+支撑力”复合测区轮轨垂向力测量方法;在感知部件结构设计上,充分考虑高速铁路主型扣件的结构特点,研制开发了结构-耦合测力传感器;在轮轨力信号拾取及传输上,设计了低功耗、小型化分布式数据采集模块,并集成5G毫米波技术,实现低时延、高可靠、大带宽数据传输。